Audio equalizer and methods for use therewith

ABSTRACT

An audio equalizer includes an equalization processor that operates in conjunction with a transformed-based audio decoder that generates a decoded audio signal from an encoded audio signal. The equalization processor receives an equalization input signal, generates a plurality of response coefficients in response to the equalization input and applies the response coefficients to partially decoded data of the transformed-based audio decoder.

CROSS REFERENCE TO RELATED PATENTS

Not Applicable

TECHNICAL FIELD OF THE INVENTION

The present invention relates to security in processing devices.

DESCRIPTION OF RELATED ART

Many audio and video systems include an audio equalizer that allows thesystem or the user to adjust the frequency response of the system to auser's tastes, to the particular environment, to the type of music thatis being reproduced, etc. The audio equalizer is traditionallyconstructed with a series of time-domain filters, either embodied inanalog circuits or digital filters. An example of such an equalizer ispresent in conjunction with US Publication No. US2004/0213339, entitled,“Equalizer”. In an audio player with a typical audio decoder that playsencoded digital audio source material, an equalizer could double the CPUusage of an audio player. In many circumstances, the implementation ofan equalizer may be too expensive or otherwise be impractical for manyreal-time audio/video systems in the consumer market.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of ordinary skill in the artthrough comparison of such systems with the present invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 presents a pictorial representation of example devices 11-17 thatcan include an audio equalizer 100 in accordance with an embodiment ofthe present invention.

FIG. 2 presents a block diagram representation of an audio equalizer 100in accordance with an embodiment of the present invention.

FIG. 3 presents a block diagram representation of a equalizationprocessor 126 in accordance with an embodiment of the present invention.

FIG. 4 presents a graphical representation of an equalization curve inaccordance with a further embodiment of the present invention.

FIG. 5 presents a graphical representation of adjusting preliminaryfilter coefficients in accordance with an embodiment of the presentinvention.

FIG. 6 presents a block diagram representation of a video decodingsystem 202 in accordance with an embodiment of the present invention.

FIG. 7 presents a block diagram representation of a video transcodingsystem 204 in accordance with an embodiment of the present invention.

FIG. 8 presents a block diagram representation of a video distributionsystem 175 in accordance with an embodiment of the present invention.

FIG. 9 presents a block diagram representation of a video storage system179 in accordance with an embodiment of the present invention.

FIG. 10 presents a flowchart representation of a method in accordancewith an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION INCLUDING THE PRESENTLY PREFERREDEMBODIMENTS

FIG. 1 presents a pictorial representation of example devices 11-17 thatcan include an audio equalizer 100 in accordance with an embodiment ofthe present invention. In particular, these example devices includedigital video recorder/set top box 11, television or monitor 12,wireless telephony device 13, computers 14 and 15, personal video player16, personal audio player 17 or other devices that include an audioequalizer.

Audio equalizer 100 operates in conjunction with a transformed-basedaudio decoder included in the host device. The audio equalizer 100generates equalizer response coefficients that are applied directly toaudio data in the frequency domain, before the audio data is fullydecoded. This approach avoids the use of complicated time-domain digitalfilters, yet is equivalent in performance to a time-domain equalizerembodied with an FIR filter of order as high as the size of frame length(1024 for AAC). In short, the audio equalizer 100 can achieve highquality equalizer effects, adapting to any desired equalizer response.In addition, since the transform-based audio decoder is already workingin frequency domain, the audio equalizer 100 needs not re-perform thesteps of transform and reverse transform, reducing the computationaleffort required to perform the equalization. In operation, the audioequalizer 100 can use as little as 0.1%˜0.2% of the processing requiredby an time-domain equalizer.

While audio equalizer 100 is shown as being integrated in each of thedevices 11-17, in an alternative embodiment of the present invention,audio equalizer 100 can be coupled to one or more of these host devicesvia a host interface. In particular, audio equalizer 100 can take on anyone of a number of form factors such as a PC card, memory card, personalcomputer memory card international association (PCMCIA) card, universalserial bus (USB) dongle or other device that is coupleable to one ormore host devices via an Ethernet connection, a memory card interface,USB connection, Firewire (IEEE 1394) connection, small computer systeminterface (SCSI), PCMCIA interface, or other interface either standardor proprietary or that is incorporated into the device 11-17.

Audio equalizer 100 will be described in greater detail in conjunctionwith FIGS. 2-10, including several optional functions and features.

FIG. 2 presents a block diagram representation of an audio equalizer 100in accordance with an embodiment of the present invention. Audioequalizer 100 includes an equalization processor 126 that operates inconjunction with a transformed-based audio decoder 120 that generates adecoded audio signal 25, such as pulse code modulated (PCM) data, froman encoded audio signal 20. For instance, the transform-based audiodecoder 120 can be a decoder that decodes an encoded audio signal thatis formatted in accordance with an audio coding method such as WindowsMedia Architecture (WMA), Motion Picture Expert Group audio layer 3(MP3), Advanced Audio Coding (AAC), Dolby Digital (AC3), or other audiocoding methodology that operates, at least partially in the frequencydomain. In particular, typical transform-based audio decoders operatebased on inverse quantization and spectral processing that producepartially decoded data in the frequency domain. A synthesis filter bank122 is included to produce an audio signal, such as decoded audio signal25, in the time domain.

In operation, equalization processor 126 receives an equalization inputsignal 30 from a user or from in a preloaded data table or other memory,not specifically shown. For instance, the equalization input 30 caninclude an equalization curve that represents the desired equalization,such as a particular equalization gain as a function of frequency.Equalization processor 126 generates a plurality of responsecoefficients 128 that reflect this desired equalization. Equalizationprocessor 126 operates in conjunction with transform-based audio decoder120 to apply the response coefficients 128 to partially decoded data. Inan embodiment of the present invention, the response coefficients aremultiplied by partially decoded frequency domain data, prior to theapplication of a filter, such as filter bank 122. This operates toadjust the partially decoded data by the desired equalization, directlyin the frequency domain.

In an embodiment of the present invention, the response coefficients 128are values in the range of 0 to 1.0 that are generated in response toequalization input 30 to represent the desired equalization gain at eachfrequency. Since the equalizer coefficients are values less than 1.0,equalization processor 126 generates a gain 130 applied to gain stage124 to adjust the decoded audio signal 25 to produce a gain adjustedaudio signal 28 at a similar sound level. It should be noted that, in afurther embodiment, the response coefficients 128 can themselves byadjusted by the calculated gain 130 to produce an output at theappropriate sound level, without the need of gain stage 124.

In an embodiment of the present invention, the transform-based audiodecoder 120, gain stage 124 and equalization processor 126 can beimplemented using a single processing device or a plurality ofprocessing devices. Such a processing device may be a microprocessor,co-processors, a micro-controller, digital signal processor,microcomputer, central processing unit, field programmable gate array,programmable logic device, state machine, logic circuitry, analogcircuitry, digital circuitry, and/or any device that manipulates signals(analog and/or digital) based on operational instructions that arestored in a memory, such as an external memory or an internal memory toeach device. In particular, when the equalization processor 126implements one or more of its functions via a state machine, digitalcircuitry, and/or logic circuitry, the memory storing the correspondingoperational instructions may be embedded within the circuitry comprisingthe state machine, analog circuitry, digital circuitry, and/or logiccircuitry. It should further be noted that while the equalizationprocessor 126 and gain stage 124 are shown as a being separate from thetransform-based audio decoder 120, the equalization processor 126 and/orgain stage 124 can be incorporated directly in the transform-based audiodecoder 120.

FIG. 3 presents a block diagram representation of an equalizationprocessor 126 in accordance with an embodiment of the present invention.The equalization processor 126 includes a response coefficient generator140, a coefficient adjustment module 144 and a gain generation module146.

The response coefficient generator 140 generates a plurality ofpreliminary response coefficients 142 based on the equalization inputsignal 30. In an embodiment of the present invention, the equalizationinput signal 30 includes a plurality of equalization settings thatrepresent, for example, a plurality of equalization filter gains. Forexample, a user of a device 11-17 may be presented with a graphical userinterface that is implemented in conjunction with that device thatallows a user to select gains (g₁, g₂, . . . g₁₀) for filters at 32 Hz,64 Hz, 128 Hz, 256 Hz, 512 Kz, 1 kHz, 2 kHz, 4 kHz, 8 kHz and 16 kHz,that represent a desired frequency response. In a further example,similar equalization filter gains or other equalization settings can beretrieved from a look-up table or memory of the device 11-17. In thisfashion, different equalization settings can be automatically employedbased on the source or other parameters of the encoded audio signal,based on parameters of the transform-based audio decoder 120 or othervariables. It should be noted that while this example describes a tenoctave equalizer, equalization input signals 30 with greater or fewersettings may likewise be employed to represent a desired frequencyresponse.

In response to the equalization filter gains or other equalizationsettings of the equalization input signal 30, the response coefficientgenerator 140 generates an equalization curve that corresponds to thedesired frequency response. In one example, the response coefficientgenerator 140 uses interpolation or other curve fitting techniques togenerate the equalization curve that fills-in gains at frequencies,intermediate to the filter frequencies, corresponding to the pluralityof preliminary response coefficients. In a further example, theequalization input signal 30 includes the equalization curve itself. Afurther example will be presented in conjunction with FIG. 4.

FIG. 4 presents a graphical representation of an equalization curve inaccordance with a further embodiment of the present invention. Anequalization curve 150 is shown that is either included in equalizationinput signal 30 of generated by response coefficient generator 140 inresponse to the equalization input signal 30. As discussed, theequalization curve 150 represents a desired frequency response of thedecoded audio signal 25, such as a 20 Hz-20 kHz frequency response.Response coefficient generator 140 generates a plurality of preliminaryresponse coefficients 142 that correspond to the frequency bins employedin the transform-based audio decoder 120. For example, the preliminaryresponse coefficients 142 can be fit to the response curve. Consideringthe example of a particular preliminary response coefficient 142 atfrequency f_(i), the gain g_(i) can be determined from the gain of theequalization curve 150 at that corresponding frequency.

It should be noted that the graph of FIG. 4 is not shown to scale andmay, for example, include many more preliminary response coefficients142 than are represented. For example, a number of preliminary responsecoefficients 142 can be determined based on the frame/window size of thetransform-based audio decoder 120. Transform-based codecs are framebased, and most of them have a fixed frame size and window size. Thenumber of preliminary response coefficients 142 can be 1024 when, forexample, the transform-based audio decoder 120 decodes an AAC encodedaudio signal 20.

While using a fixed frame size, some codecs employ different transformwindow sizes. For example, ACC employs two different window sizes of1024 and 128. To perform the same equalization for an audio stream, theequalization processor 126 needs to generate response coefficients 128for various window sizes. Returning now to FIG. 3, the equalizationprocessor 126 includes a coefficient adjustment module 144 thatgenerates the response coefficients 128 from the preliminary responsecoefficients 142, based on a window size indicator 132 received from thetransform-based audio decoder 120. This is done by scaling the number ofcoefficients to the desired window size.

The operation of coefficient adjustment module 144 can be described inthe context of the following example where the set of preliminaryresponse coefficients 142 is generated for a window size of 1024 in anAAC stream. The coefficient adjustment module 144 can pass thepreliminary response coefficients 142 as the response coefficients 128,when the window size indicator 132 indicates a full window size, such as1024. The coefficient adjustment module 144 adjusts the preliminaryresponse coefficients 142 to generate response coefficients 128 when thewindow size indicator 132 indicates a short window of size of 128. Anexample of such an adjustment by coefficient adjustment module 144 ispresented in conjunction with FIG. 5.

FIG. 5 presents a graphical representation of adjusting preliminaryfilter coefficients in accordance with an embodiment of the presentinvention. In particular, an example is shown the presents a portion ofthe preliminary response coefficients 142 for a particular equalization.In this example, coefficient adjustment module 144 adjusts thepreliminary response coefficients 142 by generating groups. Theindividual response coefficients 128 are generated by averaging thepreliminary response coefficients 142 in a corresponding group. In thisfashion, a set of 1024 preliminary response coefficients 142 can bescaled down to 128, by dividing the 1024 preliminary responsecoefficients 142 into 128 groups. The response coefficients 128 arealigned in frequency to the center of the corresponding group, with thegain being determined as the average gain from the preliminary responsecoefficients 142 in that group. While the example above describedadjustment from 1024 to a short window size of 128, the same principlecan be applied to the conversion between window sizes of different audiotypes, like AAC and MP3 with window size of 1024 and 576 respectively.It should be further noted that if conversion is from a short windowsize to a longer window size, instead of taking the average, thecoefficient adjustment module 144 can adjust the preliminary responsecoefficients 142 to interpolate new values for a larger window.

Returning again to FIG. 3, the equalization processor 126 includes again generation module 146 that generates the gain signal 130. Asdiscussed in conjunction with FIG. 2, the response coefficients 128 areapplied to the partially decoded transform data from the transform-basesaudio decoder 120. For example, the value of the data in each frequencybin can be multiplied by the response coefficient 128 at thecorresponding frequency. In an embodiment of the present invention, theresponse coefficients 128 are scaled to values from 0-1.0. In thisembodiment, the application in the response coefficients 128 results ina reduction of the over audio signal level. Gain stage 124 is includedto adjust the gain of the decoded audio signal 25 to maintain a similarsignal level in gain adjusted audio signal 28.

In an embodiment of the present invention, the gain signal 130 isdetermined by gain generation module 146 based on an averaging of atleast a subset of the plurality of response coefficients 128. Forexample, the gain G can be obtained by computing the average A of thegains g_(i) of response coefficients 128 in a limited frequency range,such as between 0˜3000 Hz, as follows:G=1/A

It should be noted further, in an alternative embodiment, gain 130 canbe applied directly to normalize the plurality of response coefficients128, if possible, avoiding the need to include gain stage 124.

FIG. 6 presents a block diagram representation of a video decodingsystem 202 in accordance with an embodiment of the present invention. Inparticular, the video decoding system 202, operates in accordance withmany of the functions and features of the H.264, MPEG-4 Part 10 AdvancedVideo Coding (AVC), or other digital format such as a Moving PictureExperts Group (MPEG) format (such as MPEG1, MPEG2 or MPEG4), VC-1 (SMPTEstandard 421M), Quicktime format, Real Media format, Windows Media Video(WMV), Audio Video Interleave (AVI), or another digital video format,either standard or proprietary or other video format. Decoding system202 operates to decode video input signals 110, that include encodedaudio signal 20 to form a processed video signal 112, that includes oris based on decoded audio signal 25 or gain adjusted audio signal 28. Inparticular, video encoding system 202 can include audio equalizer 100.

Video signal 110 and/or processed video signal 112 can be interfaced inassociation with a set-top box, television receiver, personal computer,cable television receiver, satellite broadcast receiver, broadbandmodem, 3G transceiver, a broadcast satellite system, internet protocol(IP) TV system, the Internet, a digital video disc player, a digitalvideo recorder, or other video device. In an embodiment of the presentinvention, the video signals 110 and or 112 can include a broadcastvideo signal, such as a television signal, high definition televisionsignal, enhanced high definition television signal or other broadcastvideo signal that has been transmitted over a wireless medium, eitherdirectly or through one or more satellites or other relay stations orthrough a cable network, optical network or other transmission network.In addition, the video signal 110 and/or processed video signal 112 canbe generated from a stored video file, played back from a recordingmedium such as a magnetic tape, magnetic disk or optical disk, and caninclude a streaming video signal that is transmitted over a public orprivate network such as a local area network, wide area network,metropolitan area network or the Internet.

FIG. 7 presents a block diagram representation of a video transcodingsystem 204 in accordance with an embodiment of the present invention. Inparticular, video transcoding system 204 operates in accordance withmany of the functions and features of the H.264, MPEG-4 Part 10 AdvancedVideo Coding (AVC), or other digital format such as a Moving PictureExperts Group (MPEG) format (such as MPEG1, MPEG2 or MPEG4), VC-1 (SMPTEstandard 421M), Quicktime format, Real Media format, Windows Media Video(WMV), Audio Video Interleave (AVI), high definition media interface(HDMI) or another digital video format, either standard or proprietaryor other video format. Video transcoding system 204 operates totranscode video input signals 110, that includes encoded audio signal 20to form a processed video signal 112, that includes or is based ondecoded audio signal 25 or gain adjusted audio signal 28. In particular,video transcoding system 204 can include audio equalizer 100.

As used herein, transcoding can include transrating, transcrypting,and/or transcaling the video signal 110 to generate processed videosignal 112 in addition to transcoding the video signal 110 from oneencoded audio/video format into another encoded audio/video format toform processed video signal 112. Transcoding can specifically includetranscoding the audio portion of video signal 110 to a different samplerate, encoding standard or other digital format, stereo to mono, etc.

FIG. 8 presents a block diagram representation of a video distributionsystem 175 in accordance with an embodiment of the present invention. Inparticular, processed encoded audio signal 20 is transmitted via atransmission path 322 to a video decoder 202. Video decoding system 202or video transcoding system 204, in turn can operate to decode ortranscode the encoded audio signal 20 for display on a display devicesuch as television 12, computer 14 or other display device.

The transmission path 322 can include a wireless path that operates inaccordance with a wireless local area network protocol such as an 802.11protocol, a WIMAX protocol, a Bluetooth protocol, etc. Further, thetransmission path can include a wired path that operates in accordancewith a wired protocol such as a USB protocol, high-definition multimediainterface (HDMI) protocol an Ethernet protocol or other high speedprotocol.

FIG. 9 presents a block diagram representation of a video storage system179 in accordance with an embodiment of the present invention. Inparticular, device 11 is a set top box with built-in digital videorecorder functionality, a stand alone digital video recorder, a DVDrecorder/player or other device that includes video decoding system 202or video transcoding system 204 and stores the encoded audio signal 20in storage 181 for playback on a display device such as television 12.Storage 181 can include a hard disk drive optical disk drive or otherdisk drive, read-only memory, random access memory, volatile memory,non-volatile memory, static memory, dynamic memory, flash memory, cachememory, and/or any device that stores digital information. Storage 181can be integrated in the device 11 or coupled to the device 11 via anetwork, wireline coupling or other connection.

While video encoder 200 is shown as a separate device, it can further beincorporated into device 11. While these particular devices areillustrated, video storage system 179 can include a hard drive, flashmemory device, computer, DVD burner, or any other device that is capableof generating, storing, decoding and/or displaying a video stream inaccordance with the methods and systems described in conjunction withthe features and functions of the present invention as described herein.

FIG. 10 presents a flowchart representation of a method in accordancewith an embodiment of the present invention. In particular a method ispresented for use in conjunction with one or more functions and featuresdescribed in conjunction with FIGS. 1-9. In step 400, an equalizationinput signal is received. In step 402, a plurality of responsecoefficients are generated in response to the equalization input. Instep 404, the response coefficients are applied to partially decodeddata of a transformed-based audio decoder that produces a decoded audiosignal. In optional steps 406 and 408, a gain signal is generated basedon the plurality of response coefficients and a gain of the decodedaudio signal is adjusted based on the gain signal.

In an embodiment of the present invention, the gain signal is generatedbased on an averaging of at least a subset of the plurality of responsecoefficients. Step 402 can include generating a plurality of preliminaryresponse coefficients based on the equalization input signal andgenerating an equalization curve that corresponds to the equalizationinput signal and fitting the plurality of preliminary responsecoefficients to the equalization curve. In step 402, the plurality ofresponse coefficients can be generated from the plurality of preliminaryresponse coefficients, based on a window size indicator received fromthe transform-based audio decoder. Further, in step 402, the pluralityof response coefficients can be generated by adjusting the plurality ofpreliminary response coefficients, when the window size indicatorincludes a first value. In addition, in step 402, the plurality ofresponse coefficients can be generated as the plurality of responsecoefficients, when the window size indicator includes a second value.The plurality of preliminary response coefficients can be adjusted bygenerating a plurality of groups of preliminary response coefficients,and generating each of the plurality of response coefficients based onan averaging of a corresponding one of the plurality of groups ofpreliminary response coefficients.

While particular combinations of various functions and features of thepresent invention have been expressly described herein, othercombinations of these features and functions are possible that are notlimited by the particular examples disclosed herein are expresslyincorporated within the scope of the present invention.

As one of ordinary skill in the art will further appreciate, the term“coupled”, as may be used herein, includes direct coupling and indirectcoupling via another component, element, circuit, or module where, forindirect coupling, the intervening component, element, circuit, ormodule does not modify the information of a signal but may adjust itscurrent level, voltage level, and/or power level. As one of ordinaryskill in the art will also appreciate, inferred coupling (i.e., whereone element is coupled to another element by inference) includes directand indirect coupling between two elements in the same manner as“coupled”.

As the term module is used in the description of the various embodimentsof the present invention, a module includes a functional block that isimplemented in hardware, software, and/or firmware that performs one ormore functions such as the processing of an input signal to produce anoutput signal. As used herein, a module may contain submodules thatthemselves are modules.

Thus, there has been described herein an apparatus and method, as wellas several embodiments including a preferred embodiment, forimplementing a an audio equalizer. Various embodiments of the presentinvention herein-described have features that distinguish the presentinvention from the prior art.

It will be apparent to those skilled in the art that the disclosedinvention may be modified in numerous ways and may assume manyembodiments other than the preferred forms specifically set out anddescribed above. Accordingly, it is intended by the appended claims tocover all modifications of the invention which fall within the truespirit and scope of the invention.

What is claimed is:
 1. An audio equalizer comprising: a transform-basedaudio decoder that produces a decoded audio signal from an encoded audiosignal; and an equalization processor, coupled to the transform-basedaudio decoder, that receives an equalization input signal, generates aplurality of response coefficients in response to the equalization inputsignal and applies the plurality of response coefficients to partiallydecoded frequency domain data during decoding by the transform-basedaudio decoder.
 2. The audio equalizer of claim 1, wherein theequalization processor further generates a gain signal based on theplurality of response coefficients, and wherein the audio equalizerfurther comprises: a gain stage, coupled to the equalization processor,that adjusts a gain of the decoded audio signal based on the gainsignal.
 3. The audio equalizer of claim 2, wherein the equalizationprocessor includes a gain generation module that generates the gainsignal based on an averaging of at least a subset of the plurality ofresponse coefficients.
 4. The audio equalizer of claim 1, wherein theequalization processor includes a response coefficient generator thatgenerates a plurality of preliminary response coefficients based on theequalization input signal.
 5. The audio equalizer of claim 4, whereinthe response coefficient generator generates an equalization curve thatcorresponds to the equalization input signal and fits the plurality ofpreliminary response coefficients to the equalization curve.
 6. Theaudio equalizer of claim 4, wherein the equalization processor furtherincludes a coefficient adjustment module, that generates the pluralityof response coefficients from the plurality of preliminary responsecoefficients, based on a window size indicator received from thetransform-based audio decoder.
 7. The audio equalizer of claim 6,wherein the coefficient adjustment module adjusts the plurality ofpreliminary response coefficients when the window size indicatorincludes a first value.
 8. The audio equalizer of claim 7, wherein thecoefficient adjustment module uses the plurality of preliminary responsecoefficients as the plurality of response coefficients when the windowsize indicator includes a second value.
 9. The audio equalizer of claim7, wherein the coefficient adjustment module adjusts the plurality ofpreliminary response coefficients by generating a plurality of groups ofpreliminary response coefficients, and generating each of the pluralityof response coefficients based on an averaging of a corresponding one ofthe plurality of groups of preliminary response coefficients.
 10. Amethod comprising: receiving an equalization input signal; generating aplurality of response coefficients in response to the equalization inputsignal; and applying the plurality of response coefficients to partiallydecoded frequency domain data of a transform-based audio decoder thatproduces a decoded audio signal.
 11. The method of claim 10, furthercomprising: generating a gain signal based on the plurality of responsecoefficients; and adjusting a gain of the decoded audio signal based onthe gain signal.
 12. The method of claim 11, wherein the gain signal isgenerated based on an averaging of at least a subset of the plurality ofresponse coefficients.
 13. The method of claim 10, wherein generatingthe plurality of response coefficients includes generating a pluralityof preliminary response coefficients based on the equalization inputsignal.
 14. The method of claim 13, wherein generating the plurality ofresponse coefficients includes generating an equalization curve thatcorresponds to the equalization input signal and fitting the pluralityof preliminary response coefficients to the equalization curve.
 15. Themethod of claim 14, wherein the plurality of response coefficients aregenerated from the plurality of preliminary response coefficients, basedon a window size indicator received from the transform-based audiodecoder.
 16. The method of claim 15, wherein the plurality of responsecoefficients are generated by adjusting the plurality of preliminaryresponse coefficients, when the window size indicator includes a firstvalue.
 17. The method of claim 16, wherein the plurality of responsecoefficients are generated as the plurality of response coefficients,when the window size indicator includes a second value.
 18. The methodof claim 16, wherein the plurality of preliminary response coefficientsare adjusted by generating a plurality of groups of preliminary responsecoefficients, and generating each of the plurality of responsecoefficients based on an averaging of a corresponding one of theplurality of groups of preliminary response coefficients.